Just Journalism, the organisation founded to encourage more balanced media coverage of Israel, is closing this week because of lack of funds.
Founder Dana Brass said that despite its "extremely modest" budget of £130,000 a year, "it became increasingly difficult to sustain financially the operation in the current economic environment".
She added: "We're extremely proud of all the work we have produced since we launched and of the global impact we made. The professionalism, quality and originality of our work played a unique role and earned us respect and credibility from those who followed us. We are just sorry that, at this time, the work cannot continue."
Launched in 2008, the organisation provided daily online analysis of reporting of Israel as well as publishing detailed critiques of media such as the Guardian or the London Review of Books.
Michael Weiss, who left as director - its third since the organisation's launch - in spring but continued as spokesman until a few weeks ago, said that news of the closure was "a surprise when I found out a few days earlier".
Since May, Mr Weiss has worked as communications and public relations director of the Henry Jackson Society, the association promoting liberal democracy. Just Journalism had shared offices with the society lately and several of the HJS staff served on Just Journalism's advisory board.
Robin Shepherd, international affairs director of HJS and a member of Just Journalism's advisory board, said: "This is a great pity and the cause of Israel in Britain will be the poorer for it."
Despite its problems, Just Journalism retained some loyal donors, including Conservative peer Lord Fink.